nitrogen-dioxide and 1-3-butadiene

Topics: Acetaldehyde; Air Pollutants; Air Pollution; Benzene; Cross-Sectional Studies; Female; Formaldehyde; Fossil Fuels; Humans; Hypertension; Nitrogen Dioxide; Particulate Matter

Population exposure assessment methods that capture local-scale pollutant variability are needed for large-scale epidemiological studies and surveillance, policy, and regulatory purposes. Currently, such exposure methods are limited.. We created 2006 national pollutant models for fine particulate matter [PM with aerodynamic diameter ≤ 2.5 μm (PM2.5)], nitrogen dioxide (NO2), benzene, ethylbenzene, and 1,3-butadiene from routinely collected fixed-site monitoring data in Canada. In multiple regression models, we incorporated satellite estimates and geographic predictor variables to capture background and regional pollutant variation and used deterministic gradients to capture local-scale variation. The national NO2 and benzene models are evaluated with independent measurements from previous land use regression models that were conducted in seven Canadian cities. National models are applied to census block-face points, each of which represents the location of approximately 89 individuals, to produce estimates of population exposure.. The national NO2 model explained 73% of the variability in fixed-site monitor concentrations, PM2.5 46%, benzene 62%, ethylbenzene 67%, and 1,3-butadiene 68%. The NO2 model predicted, on average, 43% of the within-city variability in the independent NO2 data compared with 18% when using inverse distance weighting of fixed-site monitoring data. Benzene models performed poorly in predicting within-city benzene variability. Based on our national models, we estimated Canadian ambient annual average population-weighted exposures (in micrograms per cubic meter) of 8.39 for PM2.5, 23.37 for NO2, 1.04 for benzene, 0.63 for ethylbenzene, and 0.09 for 1,3-butadiene.. The national pollutant models created here improve exposure assessment compared with traditional monitor-based approaches by capturing both regional and local-scale pollution variation. Applying national models to routinely collected population location data can extend land use modeling techniques to population exposure assessment and to informing surveillance, policy, and regulation.

Topics: Air Pollution; Benzene; Benzene Derivatives; Butadienes; Canada; Environmental Monitoring; Models, Theoretical; Nitrogen Dioxide

1,3-Butadiene (BD) in the atmosphere is a highly reactive hazardous air pollutant, which has a short lifetime and is quickly transformed to reaction products, some of which are also toxic. The ability to predict exposure to BD and its' products requires models with chemical mechanisms which can simulate these transformations. The atmospheric photochemical reactions of BD have been studied in the University of North Carolina Outdoor smog chamber, which has been used for over 30 years to test photochemical mechanisms for air quality simulation models for ozone. Experiments have been conducted under conditions of real sunlight and realistic temperature and humidity to study the transformations of BD and to develop and test chemical mechanisms for the simulation of these processes. Experimental observation of time-concentration data of BD decay and the formation of many products is compared to simulation results. This chemical mechanism can be incorporated into air quality simulation models which can be used to estimate ambient concentrations needed for exposure estimates.

Topics: Atmosphere; Atmosphere Exposure Chambers; Butadienes; Nitric Oxide; Nitrogen Dioxide; Oxidation-Reduction; Ozone; Photochemistry; Sunlight

A UV-irradiated mixture of 1,3-butadiene and nitrogen dioxide (NO2) was tested for its potency to induce DNA damage measured as single-strand breaks (SSB) in lungs of mice. Both gases were also tested separately. After 16 h exposure a UV-irradiated mixture of 40 ppm butadiene + 20 ppm NO2, but not 20 ppm butadiene + 10 ppm NO2 + UV, induced a significant increase in SSB as measured by the alkaline unwinding technique. There was no increase in the level of SSB using the alkaline elution technique during the same testing conditions. However, after 5 h exposure to 60 ppm butadiene + 30 ppm NO2 + UV both methods demonstrated a significant increase in SSB. Mice were also exposed to butadiene at 80 and 200 ppm for 16 h and at 500 ppm for 5 h. DNA damage was demonstrated in both liver and lung after 5 and 16 h (only at 200 ppm) of exposure using the unwinding technique. Using the alkaline elution assay, a significant increase in the level of SSB in lung and liver was found only after 5 h of exposure. When mice were exposed to 30 ppm NO2 for 16 h or 50 ppm for 5 h, a significant increase in SSB was found with the unwinding technique. Alveolar macrophages from mice were also exposed in vitro to the gas mixture and to butadiene and NO2 separately. In these experiments, the DNA damage was studied with the unwinding technique. A significant effect was demonstrated with 40 ppm butadiene + 20 ppm NO2 + UV. NO2 itself contributed to some extent to the increase. Reasons for the discrepancies between the unwinding and the alkaline elution techniques are discussed.

Topics: Air Pollutants; Alkalies; Animals; Butadienes; Chemistry Techniques, Analytical; DNA; DNA Damage; Liver; Macrophages, Alveolar; Male; Mice; Mutagens; Nitrogen Dioxide; Photochemistry; Ultraviolet Rays

The genotoxic activity of a photochemical reaction mixture of 1,3-butadiene and nitrogen dioxide was investigated in vivo in the mouse bone marrow micronucleus assay and the somatic mutation and recombination test in Drosophila (the wing spot test). Butadiene alone was not mutagenic in Drosophila, but induced micronuclei in mice at 10 ppm after 23 h of exposure. Nitrogen dioxide was not genotoxic in either test system. The photochemical reaction products were toxic but probably not mutagenic in Drosophila and not genotoxic in mouse bone marrow. The in vivo results do not confirm earlier in vitro results that demonstrated a strong direct-acting mutagenic activity of the photochemical products in Salmonella.

Topics: Animals; Bone Marrow; Butadienes; Drosophila; Female; Male; Mice; Micronucleus Tests; Mutagens; Nitrogen Dioxide; Photochemistry; Pigmentation; Recombination, Genetic